Add MediaMetadata.EMPTY

PiperOrigin-RevId: 362186928

extensions/cast/src/test/java/com/google/android/exoplayer2/ext/cast/DefaultMediaItemConverterTest.java

@@ -51,7 +51,7 @@ public class DefaultMediaItemConverterTest {
     MediaItem item =
         builder
             .setUri(Uri.parse("http://example.com"))
-            .setMediaMetadata(new MediaMetadata.Builder().build())
+            .setMediaMetadata(MediaMetadata.EMPTY)
             .setMimeType(MimeTypes.APPLICATION_MPD)
             .setDrmUuid(C.WIDEVINE_UUID)
             .setDrmLicenseUri("http://license.com")

library/common/src/main/java/com/google/android/exoplayer2/MediaItem.java

@@ -604,7 +604,7 @@ public final class MediaItem implements Bundleable {
               liveMaxOffsetMs,
               liveMinPlaybackSpeed,
               liveMaxPlaybackSpeed),
-          mediaMetadata != null ? mediaMetadata : new MediaMetadata.Builder().build());
+          mediaMetadata != null ? mediaMetadata : MediaMetadata.EMPTY);
     }
   }
 
@@ -1308,7 +1308,7 @@ public final class MediaItem implements Bundleable {
     @Nullable Bundle mediaMetadataBundle = bundle.getBundle(keyForField(FIELD_MEDIA_METADATA));
     MediaMetadata mediaMetadata;
     if (mediaMetadataBundle == null) {
-      mediaMetadata = new MediaMetadata.Builder().build();
+      mediaMetadata = MediaMetadata.EMPTY;
     } else {
       mediaMetadata = MediaMetadata.CREATOR.fromBundle(mediaMetadataBundle);
     }

library/common/src/main/java/com/google/android/exoplayer2/MediaMetadata.java

@@ -23,7 +23,7 @@ import java.lang.annotation.Documented;
 import java.lang.annotation.Retention;
 import java.lang.annotation.RetentionPolicy;
 
-/** Metadata of the {@link MediaItem}. */
+/** Metadata of a {@link MediaItem} or a playlist. */
 public final class MediaMetadata implements Bundleable {
 
   /** A builder for {@link MediaMetadata} instances. */
@@ -43,6 +43,9 @@ public final class MediaMetadata implements Bundleable {
     }
   }
 
+  /** Empty {@link MediaMetadata}. */
+  public static final MediaMetadata EMPTY = new MediaMetadata.Builder().build();
+
   /** Optional title. */
   @Nullable public final String title;